220 THE BOTANICAL MALiZINE. [VoL XXIV . No . 284# 



1909.) and in Zamia £oridana and (xnfatozamia mexicana 

 (Smith, 1907). 



Among Gnetales too 12 seems to be the prevailing number 

 e.g., 12 in Ephedra trifurca (Land, 1904.) and in Gnetum 

 Gnemon (Coulter, 1908). 



From this brief sketch in almost all Gymnospermic members 

 in which the number of chromosomes has been examined by 

 various authors, the number of chromosomes is strikingly 

 constant, so far as the data available at present show. This 

 fact of constancy of the number of chromosomes may well be 

 one of the manifestations of a common character of these 

 phyla of Gymnosperms, and may show that they represent a 

 comparatively stable organic group, not disposed to changes or 

 mutation, that is, after Rosa to be in a state of much reduced 

 variability or mutability at the present geological epoch. 



If this provisional formulation based on one of the features 

 of the fundamental cell structure, proves in future to have some 

 truth in it, this constancy in number of .chromosomes is to 

 foretell the fortune of Gymnosperms in a brief manner. 



It is true that the number of chromosomes of plants, as 

 shown by the recent investigations of various authors, is not 

 so constant as it was formerly believed ; and it may vary even 

 in one and the same individual, so that not a great weight 

 should be placed on it. But this very state of variability in a 

 number of plants may mean that they arc plants more or less 

 capable of changes or mutation. 



